Hi,

I've got two different brands of 15mm linear profile rail (one Chinese import, one SBC Linear). Both have identical mounting holes that are 4.5mm dia. with a countersunk hole for the bolt head 7.5mm dia.

I'm not sure what bolts I am supposed to use here?

M4 would fit through the hole, but all M4 bolts with a countersink are 8mm dia. on the head so they don't fit. An M4 cap head would fit the hole but it doesn't seem right to use that on a countersunk hole because the contact patch will only be on the edge on the head.

Am I supposed to use some kind of imperial size?


Thanks!